require_once the literal text require_once (case insensitive) .any character (except for line terminators)
\$the literal $ (3610 / 448 / 2416)
doc_root the literal text doc_root (case insensitive) .any character (except for line terminators)
\.the literal . (4610 / 568 / 2E16)
.any character (except for line terminators)
\\the literal \ (9210 / 1348 / 5C16)
"the literal " (3410 / 428 / 2216)
g modifier: global. Finds all matches instead of stopping after the first
m modifier: multiline. Causes ^ and $ to match the start and end of each line, not only the start and end of the string
i modifier: insensitive. Matches without distinguishing uppercase and lowercase letters
x modifier: extended. Ignores unescaped whitespace and comments outside character classes